As one of important units of electronic systems, oscillators are widely applied. Generally, power consumption and phase noise of an oscillator are main parameters for measuring performance of the oscillator, and oscillators having low power consumption and low phase noise have been a long-term research subject.
In other approaches, a cross coupled negative resistance oscillator (oscillator hereinafter) is provided. As shown in FIG. 1A, the oscillator includes a resonance unit 10 and a cross-complementing active unit 11 connected to the resonance unit 10. The resonance unit 10 is configured to generate oscillation signals having a particular oscillation frequency. The cross-complementing active unit 11 is configured to compensate for energy consumption of the resonance unit 10 such that the resonance unit 10 can output stable oscillation signals.
A calculation formula of phase noise of the oscillator is:
                                          L            ⁢                          {                              Δ                ⁢                                                                  ⁢                ω                            }                                =                                                                                          i                    n                    2                                    /                  Δ                                ⁢                                                                  ⁢                f                                            2                ⁢                                                                  ⁢                                  q                  max                  2                                                      ×                                          Γ                                  eff                  ,                  rms                                2                                            Δ                ⁢                                                                  ⁢                                  ω                  2                                                                    ,                            (        1        )            where Δω is a frequency offset of a carrier processed or generated by the oscillator, in2/Δf is power spectral density of current noise, Γeff,rms2 is a root mean square value of a Γeff (ωt) function, and qmax is a maximum charge amount of a current noise source, and:Γeff(ωt)=Γ(ωt)×α(ωt)  (2),where Γ(ωt) is an impulse sensitivity function (ISF), α(ωt) is noise-modulating function (NMF) in which a phase changes over time, and the ISF describes an offset degree of a phase of an output signal that is caused by injecting a unit pulse current into a node at a time point. Because a waveform of an oscillation signal generated by the cross coupled negative resistance oscillator shown in FIG. 1A is a sine wave, an ISFeff (that is, Γeff (ωt) in the formula (2)) function curve, as shown in FIG. 1B, of the cross coupled negative resistance oscillator is obtained by injecting a unit pulse current into the cross coupled negative resistance oscillator at different time points and then performing simulation. It can be seen from FIG. 1B that a value of the ISFeff is 0 only in a time length of π/2 (that is, from 3π/2 to 2π) within an oscillation period (2π), and is not 0 in the rest time length of 3π/2 (that is, from 0 to 3π/2). It can be known with reference to the formula (1) and the formula (2) that within the oscillation period, the phase noise of the cross coupled negative resistance oscillator is relatively high. Consequently, phase noise performance of the cross coupled negative resistance oscillator is relatively poor.